Some mechanisms of the indirect response to the nutritive density (kcal/ml) of meals by duodenal receptors have been demonstrated. These receptors determine the rate of gastroduodenal transfer of the food. In general, the greater the energy density of food, the more rapid is its rate of transfer to the duodenum and, in infants, the greater is their food intake. Obese adults prefer food of high energy density; this finding is consistent with the duodenal receptors also playing a part in causing overweight adults to have a high food intake. It is proposed to analyze the mechanism whereby in lean subjects the rate of gastroduodenal transfer of food increases with body weight. Saline test meals test the gastric propulsive component, and solutions of glucose show the duodenal inhibitory component of the mechanism of gastroduodenal transfer. The same experiments will be performed in obese subjects. The relation between the energy density of test meals, the rate of gastroduodenal transfer of food, and body habitus will be determined in lean and overweight subjects. With test meals having the volume and energy density preferred by both groups of subjects for their ordinary meals, the rate of gastroduodenal transfer will be measured in lean and overweight subjects. The objectives are to gain an understanding in depth of the relation between the characteristics of a subject's freely chosen food, its gastroduodenal transfer, and his body habitus. These facts should be of value in devising appropriate treatment for obesity.